1. Field of the Invention
The present invention relates to a functional polyurethane prepolymer, a method of preparing polyurethane by using the functional polyurethane prepolymer, and an application method thereof, in particular to a functional polyurethane prepolymer prepared by a non-isocyanate route, a method of preparing polyurethane by a using the functional polyurethane prepolymer, and an application method thereof.
2. Description of Related Art
Polyurethane (PU) is a common polymer material widely used as a sports cushion material, an elastomer material, an adhesive material, a waterproof material or a coating material.
In a conventional PU preparation process, the PU is synthesized by using isocyanates (such as diisocyanates and polyisocyanates) and polyols (such as diols or polyhydroxy polyols with high functionality) as major raw materials, but the manufacturing process of this sort usually requires phosgene which is a severely toxic pollutant. If the phosgene is leaked accidentally during the manufacturing process, the phosgene will pose an immediate threat to our environment and jeopardize our health such as causing pulmonary edema, and the manufacturing process itself will lead to a certain degree of risk. Therefore, scientists attempt to use non-isocyanates routes (which use absolutely no isocyanates at all) to manufacture polyurethane (PU).
In 1993, Takeshi Endo proposed a PU manufacturing method without using any diisocyanates, wherein five-membered cyclic carbonates (Bis(cyclic carbonate)s) and primary amines are reacted at room temperature to produce a high yield of β-position hydroxyl PU (2-Hydroxyethylurethane), and the reaction is represented by the following chemical equation:

Typically, the starting material (cyclic carbonate) of hydroxyl PU is prepared by a nucleophilic ring opening reaction of oxirane and carbon dioxide. As indicated in past literatures, cyclic carbonate is mainly prepared by a reaction of oxirane, carbon dioxide, and a catalyst at high pressure, and the common catalysts include amine, phosphine, quaternary ammonium salt, antimony compound, porpyrin and transition metal complex, and the manufacturing conditions and process involve a high level of difficulty. Until recent years, the ring opening reaction of oxirane and carbon dioxide taken place at normal pressure (1 atmosphere) was developed.
Professor Takeshi Endo, et al. further published a preparation of hydroxyl PU by using di-functional amines and di-functional cyclic carbonates, and subsequent research reports related to the ring opening reaction of cyclic carbonates provided the related reaction conditions, and specifically pointed out that the ring opening reaction has a high chemoselectivity, and will not be affected by existing water, alcohols, or esters, so that the cyclic carbonate can be reacted with a compound containing a primary amine under appropriate reaction conditions for a ring-opening polymerization, and the reaction is represented by the following chemical equations:

However, the aforementioned method is developed for the PU prepolymer with an amino functional group at an end and having a maximum average molecular weight falling within the range from 5000 g/mole to 8000 g/mole. The ring opening reaction process of the aforementioned method requires a time (20 hours or more), and this product cannot be applied for a coating application directly and effectively.